Spring applied electromagnetically released brake



May 2, 1950 R. G. LETOURNEAU 2,506,028 SPRING APPLIED ELECTROMAGNETICALLY RELEASED BRAKE Filed Aug. 24, 1945 4 Sheets-Sheet l q a N Q Y w 1 INVENTOR J- I L R, G. .LeTourneau ATTORNEYS y 1950 R. G. LETOURNEAU 2,506,028

SPRING APPLIED ELECTROMAGNETICALLY RELEASED BRAKE Filed Aug. 24, 1945 4 Sheets-Sheet 2 INVENTOR R. G. LeTbuz-neau av {all m ATTORNEYS y 1950 R. G. LETOURNEAU 2,506,028

SPRING APPLIED ELECTROMAGNETICALLY RELEASED BRAKE Filed Aug. 24, 1945 4 Sheets-Sheet Fab. 3

INVENTOR ATTORNEYS R. G.L8T0urneaw v M y 1950 R. e. LETOURNEAU 2,506,028

SPRING APPLIED ELECTROMAGNETICALLY RELEASED BRAKE Filed Aug. 24, 1945 4 Sheets-Sheet 4 a a a a REVERSING RELAY 4ND JUNCTION BOX 0 0 I INVENTOR. R. G LeYZvurneau HTTYS Patented May 2, 1950 SPRING APPLIED ELECTROMAGNETICALLY RELEASED BRAKE Robert G. Le Tourneau, Peoria, 111., assignor to R. G. Le Tourneau, Inc., Stockton, Cali, a corporation of California Application August 24, 1945, Serial No. 612,329

1 Claim.

This invention relates to, and it is an object to provide, an electric power unit or actuator of novel design; such electric power unit being adapted for commercial and industrial uses, such as the control or actuation of the moving parts of earth working scrapers, cranes, road graders, or the like.

Another object of the invention is to provide an electric power unit which comprises, in unitary, compact relation, a reversible electric motor, a reduction gear box at one end of the motor, and an electrically controlled brake at the other end of the motor; the brake being automatically released upon energization of the motor for rotation in either direction.

A further object of the invention is to provide an electric brake, as in the preceding paragraph, which is of simple and yet sturdy and practical construction; such brake being normally spring-engaged or set, and electrically released by an electromagnet associated therewith.

An additional object is to. provide an electric power unit including novel circuit breaking means whereby the motor can be shut off and the brake automatically set upon the motor making a predetermined number of revolutions after starting. This feature is important as it provides automatic and desirable means to limit the extent of movement of a part to which the electric power unit is connected in actuating relation.

A further object of the invention is to provide an electric power unit which is exceedingly effective for the purposes for which it is designed.

These objects are accomplished by means of such structure and relative arrangement of parts as will fully appear by a perusal of the following specification and claim.

In the drawings similar characters of reference indicate corresponding parts in the several views:

Figure 1 is a side elevation of the electric power unit; the reduction gear unit being shown in section.

Figure 2 is an enlarged fragmentary sectional elevation of the electrically controlled brake unit and the adjacent end of the electric motor.

Figure 3 is an enlarged fragmentary cross section showing the drive shaft of the automatic circuit breaking unit.

Figure 4 is an end elevation of one embodiment of the automatic circuit breaking unit.

Figure 5 is an end elevation showing a modified embodiment of the automatic circuit breaking unit.

Figure 6 is a diagram of one form of circuit which may be used to control the electric power un Referrin now more particularly to the characters of reference on the drawings, the electric power unit includes a reversible electric motor, indicated at I, disposed within a motor housing 2. At one end the motor housing 2 includes an end hell 3 formed as an inner end portion of an axially outwardly extending gear box 4; the latter housing a reduction gear train, indicated generally at 5. The motor shaft 6 drives the reduction gear train 5 and in turn the latter drives an output shaft 1 journaled in the gear box 4 in bearings 8, and projecting out of one end of said gear box through a seal 9. The output shaft 1 may be coupled, in any suitable manner, to the part to be actuated. For example, said outnut shaft 1 may be fitted with a cable drum having a cable leading from the drum to the movable part. This type of adaptation is illustrated in co-pending application, Serial No. 604,257, filed July 10, 1945, now U. S. Patent 2,477,811.

At the end of the motor opposite the reduction gear box 4 there is provided an electrically controlled brake unit l0 arranged, in the following manner, to normally brake the motor I against rotation:

At said end of the motor the same is formed with an end bell ll, through which the corresponding end of the motor shaft 6 projects through seals l2'as an extension 13. The end bell H is formed in concentric relation to the motor shaft extension [3 with an outwardly projecting neck It having an annular channel I5 formed therein, said channel opening outwardly and having a heavy-duty electro-magnet coil l6 seated therein.

A fixed annular head plate I! is dis osed in spaced relation outwardly of, but in generally concentric facing relation to, the outer end of the neck l4: said head plate I! being supported from the end bell II, at circumferentially spaced points, by fixed studs I 8 disposed parallel to, but radially out from, the motor shaft extension l3 Between the fixed head plate l1 and the electro-magnet coil l6 there is provided a brake assembly comprising the following:

A rotatable, intermediate brake disc I! extends radially of the motor shaft extension I! between the head plate l1 and coil l6; said intermediate brake disc including a hub 20 splined on the motor shaft extension l3 for sliding axially'of the latter.

A non-rotatable, outer brake disc 2i is disposed between the intermediate brake disc l6 and the .head plate l1, and is of somewhat greater diameter than the intermediate brake disc l9, whereby the studs l8 pass in relatively slidabl'e relation through matching openings 22 in said outer brake disc, sothat the latter is axially movable. Axial movement of the outer brake disc 2| .is controlled by a brake adjustment screw 23 ings 21 through which the studs l6 relatively slidably project, and a central opening for hub 26.

Heavy-duty compression springs 28 encircle the studs l8 and engage between the inner brake disc 26 and the adjacent portion of the end bell Ii, saidsprings normally urging the inner brake disc 26 away from the coil l6, and clamping the intermediate brake disc IS between said inner brake disc 26 and the outer brake disc 2|. intermediate brake disc I6 is formed on opposite faces with suitable brake lining 26. As the intermediate brake disc I6 is normally held against rotation by the thrust of the springs 26, the motor shaft extension |3 and the shaft 6, together with the reduction geartrain 6 and output-shaft I, are all normally locked against rotation.

By means of a suitable circuit, an illustration of one form ofwhich is shown 'inFig. 6. and which will hereinafter be described. the reverisble electric motor .I' may be energized to rotate in one direction or the other. At the same time, and regardless of the direction of-rotation of the reversible electric motor i, the electro-magnet coil [6 is energized and the resulting electromagnetic force draws theinner brake .disc 26a:-

ially inwardly against the compression of springs 26 and 'away from the intermediate brake disc ls. When this occurs said intermediate brake i9 is released and it rotates freely with the motor shaft 6. When the motor I is deenergized'the circuit to the coil i6 is automatically broken, I .whereupon the inner brake disc 26 is again urged axially outwardly by the springs '26, clamping the 'lined intermediate brake disc l9 between said inner brake disc 26 and the outer brake disc 2|. This instantaneously stops the motor I and prevents any overrunningof the output shaft 1.

In order toprevent the intermediate brake I 1 disc I! from becoming permanentlymagnetized by the coil I6, said intermediate brake disc I! is of anon-magnetic material, such as an aluminum or brass alloy.' This isimportantfor the reason that if said intermediate brake .disc" H were of a magnetic material it would 'become. permanentlymagnetized from'the coill6, with the result that said disc is would tend to follow the inner brake disc-.26, and the brake could not ever be'completelyreleased. As a further-means to prevent'such latter, and which might occurif'thedevice were set in a 'verticalposition' with the brake uppermost, a' compression spring 36 is'engaged'in a The - interlinediate brake disc l9 from following the inner brake 'disc' 26 to brake release position of the pri 36 would be insuiiicient to lift disc l6 into contact with the outer brake disc 2|.

Adjustment of the above described brake assembly is accomplished through the medium of the brake adjustment screw 23 and the hand wheel 26 thereon. A spring-pressed pin 32 works against the adjustment screw 23 and normally maintains the latter against accidental rotation.

of this invention also includes a novel circuit breaking means whereby the motor is shut off and the brake automatically set upon the motor making a predetermined number of revolutions lowing:

Within the gear box 4 the reduction gear train 6 includes a worm gear 33 on the output shaft i, and a worm pinion 64 meshes with said worm gear 33 at the bottom; said pinion being fixed '20 on a driven shaft 36 which extends through one side of the gear box 8 to a termination outwardly thereof.

At its outer end the shaft 35 has a disc 36' fixed thereon. In the embodiment of Fi 4' the circuit breaking means includes one or more stops 3? circumferentially adjustably secured on the disc 36 and projecting radially outwardly therefrom. A single pole double throw switch 38 is disposed radially out from but adjacent the disc 36, and said switch includes a switch lever 69 movable in one direction to open the switch on one side, and movable in the other direction to open the switch on the other side, as indicated by the arrow in Fig. 4.

The stops are set on the disc 36 so as to engage and move the switch lever 39 upon a predetermined-number of rotations of the shaft 1 in either direction from a given starting position.

The embodiment of the circuit breaking means shown in Fig. 5 is similar to that described above in connection with Fig. 3, but here the disc and stop arrangement is such as to permit of more than one revolution of the disc 36 before the circuit is automatically broken. In this embodiment the switch 46, which corresponds to the switch 38 in Fig.- 4, is spaced from the disc 36 out of the path of a circumferentially adjustable, laterally outwardly projecting stop 4!. A finger 42 is swingably mounted on the shaft $5v outwardly of the disc 38 and projectsacross the path of rotation of the stop-6i to a term nation at its outer 'end a suilicient distanceto en a e the switch dicated by the arrow; and in the same manner as the switch lever 36. when stop 4! is engaged with one side of finger 42 and is moving in a clockwise d rection as shown in fullline in. Fig. 5, continued movement of the stop in said direction will causethefinger to trip switch lever. 43. with a reverse movement of the discand stop, it'will be obvious that nearly two revolutions of the disc must take place before the stop will have engaged 1 the finger on the opposite side and moved the same to a switch operating position, as indicated 5mdotted lines in mg. 5. In thisnianner the circuit breaking. means can be set to funct on only upon occurrence of more than a. full revolution'of the disc 36, and which. maybe desirable under-conditions wherein the part tobe moved by 70 the electric power unit travels a substantially great distance. v v i a The illustrative circuit. shown diagrammatical- .ly in Fig. 6 comprises the-following:

vThe electric power unit which is the subject after starting; such means comprising the follever 43, which hasmovement two ways, as in- Current from a source such as a generator 46 76 feedsthrough a circuit to a reversing relay l8 which feeds current, selectively, through wires 41 V I! or 48, and simultaneously to the co l I6 through the wire 50, by a control circuit which includes separate wires 52 adapted to be selectively energized by an operator-controlled single pole doublethrow switch 53 connected to the generator A on the side opposite the ground.

This control circuit is, however, subject to a sub-circuit which includes a pair of wires 54 which lead from the reversing relay to opposite contacts 55 and 56 of the switch 38, and which contacts are adapted to be broken separately,

dependent upon the direction of swinging of the switch lever 39. On the side opposite the wires 54 the contacts 55 and 88 lead to a common ground 51, the lead between said contacts and the ground having a thermal motor protector 5| interposed therein. The arrangement is such that when either the contacts 55 or 58 are broken a corresponding side of the feed circu t of wires 41 and 48 to the motor I is simultaneously broken, along with the circuit to the coil l6, through the medium of .instrumentalities within the reversing relay, Thus, when the stop means 31 on the disc 36, in the embodiment of Fig. 4, engage the switch lever 39 on one side or the other, resulting in opening of the contacts 55 or 58, depending on the direction of rotation of said disc 38, the motor l is immediately deenergized and the brake applied, caus ng instantaneous stoppage of rota tion 01' the output shaft 1.

From the foregoin description it will be readily seen that there has been produced such a device as substantially fulfills the objects of the invention as set forth herein.

While this specifica ion sets forth in detail the An electrically controlled brake for an electric motor comprising in combination with said motor, a group of concentric brake discs supported coaxially with the motor shaft adjacent one end thereof, one disc including a hub slidably mounted on r the motor shaft and rotatable therewith, said shaft terminating within the hub, a normally fixed non-rotatable disc on one sde of the first disc and a floating non-rotatable disc on the opposite side of said first disc, yieldable means normally urging all of said discs into engagement with each other, electrically actuated means operative to cause relative separation of said, first and third named discs, and yieldable means interposed between the motor shaft and the first named disc of suillcient tension to prevent the first named disc from dragging on the third disc as the latter is moved away from said first disc but insufllcient to force the said first disc into frictional contact with the second named disc; said yieldable means including ahead in the bore of said hub outwardly of the adjacent end of the motor shaft, there being an axial socket bore in the shaft open to said end, and a compression spring seated in said socket bore at one end portion and engaging at the other end against such head.

ROBERT G. LE TOURNEAU.

REFERENCES CITED The following references are of record in the flle of this patent:

UNITED STATES PATENTS Number Name Date 339,697 Roucaglia u Apr. 3, 1886 688,670 McGeorge Dec. 10, 1901 867,483 Darlington Oct. 1, 1907 1,212,981 Maris Jan. 16, 1917 1,656,174 Dahl Jan. 17, 1928 1,852,574 Howe Apr, 5, 1932 1,884,863 Remde Oct. 25, 1932 1,967,044 Van Den Eynde July 17, 1934 1,968,583 Apple July 31, 1934 2,180,287 Zwack Nov. 14, 1939 2,188,766 Buckley Jan. 30, 1940 2,214,807 Buckley Sept. 17, 1940 2,292,704 Lillquist Aug. 11, 1942 2,302,826 Wilson Nov. 24, 1942 2,368,317 Meyer et al Jan. 30, 1945 FOREIGN PATENTS Number Country Date Great Britain Jan. 2, 1936 

